Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270112037602/sk3448sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270112037602/sk3448Isup2.hkl | |
Chemical Markup Language (CML) file https://doi.org/10.1107/S0108270112037602/sk3448Isup3.cml |
CCDC reference: 906575
For related literature, see: Allen (2002); Allen et al. (1995); Atria et al. (2010); Atria, Astete, Garland & Baggio (2011); Atria, Garland & Baggio (2011); Miao et al. (2007).
Crystals of the title compound were obtained as a by-product during the synthesis of a family of lanthanide complexes with crotonic acid and isoquinolin-5-amine. To an aqueous solution (200 ml) containing the corresponding lanthanide oxide (1 mmol), an aqueous solution (20 ml) of crotonic acid (6 mmol) was added, followed by the isoquinolin-5-amine ligand (1 mmol) dissolved in ethanol (30 ml). The resulting mixture was refluxed for 8 h and filtered. The filtrate was allowed to evaporate at room temperature; in one of the attempts made, good single crystals of (I) suitable for X-ray analysis were unwittingly obtained.
The absolute structure could not be determined for this light-atom structure. All H atoms were clearly seen in a difference Fourier map but were treated differently in the refinement. C-bound H atoms were repositioned at their expected locations and allowed to ride, with C—H = 0.95 Å. N-bound H atoms, displaying a noticeable pyramidality, were refined with similarity restraints in the internal distances in both molecules (s.u. on N—H bonds = 0.015 Å and s.u. on H···H distances = 0.025 Å). In all cases, H atoms were treated with Uiso(H) = 1.2Ueq(parent).
Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT (Bruker, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).
C9H8N2 | F(000) = 608 |
Mr = 144.17 | Dx = 1.304 Mg m−3 |
Monoclinic, Cc | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: C -2yc | Cell parameters from 2008 reflections |
a = 6.0731 (15) Å | θ = 2.5–25.2° |
b = 14.921 (4) Å | µ = 0.08 mm−1 |
c = 16.285 (4) Å | T = 150 K |
β = 95.686 (4)° | Block, pink |
V = 1468.5 (7) Å3 | 0.36 × 0.19 × 0.12 mm |
Z = 8 |
Bruker SMART CCD area-detector diffractometer | 3082 independent reflections |
Radiation source: fine-focus sealed tube | 2701 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.020 |
CCD rotation images, thin slices scans | θmax = 27.8°, θmin = 2.5° |
Absorption correction: multi-scan (SADABS in SAINT-NT; Bruker, 2002) | h = −7→7 |
Tmin = 0.98, Tmax = 0.99 | k = −19→19 |
6002 measured reflections | l = −21→21 |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.038 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.090 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.04 | w = 1/[σ2(Fo2) + (0.0471P)2 + 0.1477P] where P = (Fo2 + 2Fc2)/3 |
3082 reflections | (Δ/σ)max < 0.001 |
215 parameters | Δρmax = 0.15 e Å−3 |
9 restraints | Δρmin = −0.16 e Å−3 |
C9H8N2 | V = 1468.5 (7) Å3 |
Mr = 144.17 | Z = 8 |
Monoclinic, Cc | Mo Kα radiation |
a = 6.0731 (15) Å | µ = 0.08 mm−1 |
b = 14.921 (4) Å | T = 150 K |
c = 16.285 (4) Å | 0.36 × 0.19 × 0.12 mm |
β = 95.686 (4)° |
Bruker SMART CCD area-detector diffractometer | 3082 independent reflections |
Absorption correction: multi-scan (SADABS in SAINT-NT; Bruker, 2002) | 2701 reflections with I > 2σ(I) |
Tmin = 0.98, Tmax = 0.99 | Rint = 0.020 |
6002 measured reflections |
R[F2 > 2σ(F2)] = 0.038 | 9 restraints |
wR(F2) = 0.090 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.04 | Δρmax = 0.15 e Å−3 |
3082 reflections | Δρmin = −0.16 e Å−3 |
215 parameters |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
x | y | z | Uiso*/Ueq | ||
N11 | 0.1181 (3) | 0.75791 (11) | 0.71764 (10) | 0.0353 (4) | |
N21 | 0.4601 (3) | 0.44916 (11) | 0.66851 (11) | 0.0350 (4) | |
H21A | 0.506 (3) | 0.3929 (10) | 0.6840 (14) | 0.050 (7)* | |
H21B | 0.573 (3) | 0.4876 (12) | 0.6624 (13) | 0.035 (6)* | |
C11 | 0.0040 (3) | 0.69540 (13) | 0.75160 (11) | 0.0322 (4) | |
H11 | −0.1212 | 0.7141 | 0.7778 | 0.039* | |
C21 | 0.0527 (3) | 0.60266 (12) | 0.75230 (10) | 0.0268 (4) | |
C31 | −0.0814 (3) | 0.53979 (12) | 0.78932 (11) | 0.0310 (4) | |
H31 | −0.2082 | 0.5590 | 0.8143 | 0.037* | |
C41 | −0.0260 (3) | 0.45095 (12) | 0.78871 (12) | 0.0339 (4) | |
H41 | −0.1137 | 0.4084 | 0.8142 | 0.041* | |
C51 | 0.1587 (3) | 0.42216 (12) | 0.75093 (12) | 0.0319 (4) | |
H51 | 0.1932 | 0.3601 | 0.7514 | 0.038* | |
C61 | 0.2921 (3) | 0.48055 (12) | 0.71302 (11) | 0.0275 (4) | |
C71 | 0.2413 (3) | 0.57451 (12) | 0.71441 (10) | 0.0255 (4) | |
C81 | 0.3646 (3) | 0.64207 (13) | 0.67857 (11) | 0.0296 (4) | |
H81 | 0.4924 | 0.6266 | 0.6525 | 0.036* | |
C91 | 0.2998 (3) | 0.72951 (12) | 0.68152 (12) | 0.0326 (4) | |
H91 | 0.3860 | 0.7733 | 0.6570 | 0.039* | |
N12 | 0.1848 (3) | 1.14060 (11) | 0.49255 (10) | 0.0350 (4) | |
N22 | 0.5738 (3) | 0.83554 (11) | 0.53578 (11) | 0.0327 (4) | |
H22A | 0.619 (3) | 0.7791 (9) | 0.5251 (12) | 0.027 (5)* | |
H22B | 0.683 (3) | 0.8765 (11) | 0.5468 (13) | 0.039 (6)* | |
C12 | 0.0535 (3) | 1.07705 (13) | 0.45894 (11) | 0.0311 (4) | |
H12 | −0.0870 | 1.0948 | 0.4333 | 0.037* | |
C22 | 0.1057 (3) | 0.98471 (13) | 0.45819 (10) | 0.0264 (4) | |
C32 | −0.0439 (3) | 0.92095 (12) | 0.42084 (11) | 0.0304 (4) | |
H32 | −0.1851 | 0.9390 | 0.3961 | 0.036* | |
C42 | 0.0172 (3) | 0.83286 (12) | 0.42081 (12) | 0.0339 (4) | |
H42 | −0.0821 | 0.7897 | 0.3952 | 0.041* | |
C52 | 0.2243 (3) | 0.80513 (12) | 0.45795 (12) | 0.0317 (4) | |
H52 | 0.2616 | 0.7433 | 0.4570 | 0.038* | |
C62 | 0.3758 (3) | 0.86487 (12) | 0.49587 (10) | 0.0270 (4) | |
C72 | 0.3174 (3) | 0.95793 (11) | 0.49562 (10) | 0.0248 (4) | |
C82 | 0.4575 (3) | 1.02669 (12) | 0.53050 (11) | 0.0299 (4) | |
H82 | 0.6009 | 1.0123 | 0.5558 | 0.036* | |
C92 | 0.3873 (3) | 1.11346 (12) | 0.52790 (12) | 0.0328 (4) | |
H92 | 0.4852 | 1.1579 | 0.5522 | 0.039* |
U11 | U22 | U33 | U12 | U13 | U23 | |
N11 | 0.0388 (10) | 0.0267 (8) | 0.0405 (9) | 0.0029 (7) | 0.0042 (7) | 0.0015 (7) |
N21 | 0.0298 (9) | 0.0296 (9) | 0.0463 (10) | 0.0056 (8) | 0.0073 (7) | −0.0013 (8) |
C11 | 0.0328 (10) | 0.0298 (10) | 0.0341 (10) | 0.0052 (8) | 0.0044 (8) | 0.0007 (8) |
C21 | 0.0272 (9) | 0.0272 (9) | 0.0251 (8) | 0.0005 (7) | −0.0013 (7) | 0.0007 (7) |
C31 | 0.0277 (10) | 0.0335 (10) | 0.0318 (10) | −0.0005 (8) | 0.0030 (8) | 0.0009 (8) |
C41 | 0.0343 (10) | 0.0323 (10) | 0.0349 (10) | −0.0062 (8) | 0.0026 (8) | 0.0048 (8) |
C51 | 0.0356 (10) | 0.0220 (9) | 0.0369 (10) | −0.0003 (8) | −0.0024 (8) | 0.0015 (8) |
C61 | 0.0278 (9) | 0.0260 (10) | 0.0277 (9) | 0.0034 (7) | −0.0023 (7) | −0.0017 (7) |
C71 | 0.0243 (9) | 0.0275 (9) | 0.0236 (8) | 0.0021 (7) | −0.0029 (7) | −0.0009 (7) |
C81 | 0.0266 (9) | 0.0338 (10) | 0.0283 (9) | −0.0010 (7) | 0.0021 (7) | −0.0002 (8) |
C91 | 0.0353 (10) | 0.0285 (10) | 0.0336 (10) | −0.0044 (8) | 0.0013 (8) | 0.0026 (8) |
N12 | 0.0364 (8) | 0.0285 (8) | 0.0397 (9) | 0.0046 (7) | 0.0017 (7) | −0.0021 (7) |
N22 | 0.0291 (8) | 0.0249 (9) | 0.0443 (9) | 0.0055 (7) | 0.0045 (7) | 0.0045 (7) |
C12 | 0.0300 (9) | 0.0295 (10) | 0.0335 (10) | 0.0056 (8) | 0.0014 (8) | −0.0011 (8) |
C22 | 0.0268 (9) | 0.0290 (10) | 0.0241 (9) | 0.0025 (7) | 0.0057 (7) | 0.0005 (7) |
C32 | 0.0257 (9) | 0.0344 (10) | 0.0309 (10) | −0.0016 (8) | 0.0027 (8) | 0.0004 (8) |
C42 | 0.0341 (10) | 0.0309 (10) | 0.0372 (10) | −0.0088 (8) | 0.0059 (8) | −0.0041 (8) |
C52 | 0.0351 (11) | 0.0212 (9) | 0.0397 (10) | 0.0003 (8) | 0.0089 (8) | −0.0007 (8) |
C62 | 0.0291 (9) | 0.0250 (9) | 0.0282 (9) | 0.0025 (7) | 0.0093 (7) | 0.0021 (7) |
C72 | 0.0277 (9) | 0.0240 (9) | 0.0234 (8) | 0.0017 (7) | 0.0059 (7) | 0.0006 (7) |
C82 | 0.0275 (9) | 0.0323 (10) | 0.0296 (9) | 0.0001 (8) | 0.0009 (7) | −0.0012 (8) |
C92 | 0.0336 (10) | 0.0290 (9) | 0.0349 (10) | −0.0005 (8) | −0.0012 (8) | −0.0042 (8) |
N11—C11 | 1.316 (2) | N12—C12 | 1.322 (3) |
N11—C91 | 1.368 (2) | N12—C92 | 1.366 (3) |
N21—C61 | 1.390 (2) | N22—C62 | 1.380 (2) |
N21—H21A | 0.913 (13) | N22—H22A | 0.907 (13) |
N21—H21B | 0.907 (13) | N22—H22B | 0.907 (13) |
C11—C21 | 1.415 (3) | C12—C22 | 1.414 (3) |
C11—H11 | 0.9500 | C12—H12 | 0.9500 |
C21—C31 | 1.415 (3) | C22—C32 | 1.411 (3) |
C21—C71 | 1.417 (2) | C22—C72 | 1.424 (2) |
C31—C41 | 1.368 (2) | C32—C42 | 1.366 (3) |
C31—H31 | 0.9500 | C32—H32 | 0.9500 |
C41—C51 | 1.399 (3) | C42—C52 | 1.403 (3) |
C41—H41 | 0.9500 | C42—H42 | 0.9500 |
C51—C61 | 1.377 (3) | C52—C62 | 1.382 (3) |
C51—H51 | 0.9500 | C52—H52 | 0.9500 |
C61—C71 | 1.436 (2) | C62—C72 | 1.433 (2) |
C71—C81 | 1.416 (2) | C72—C82 | 1.416 (2) |
C81—C91 | 1.365 (3) | C82—C92 | 1.362 (3) |
C81—H81 | 0.9500 | C82—H82 | 0.9500 |
C91—H91 | 0.9500 | C92—H92 | 0.9500 |
C11—N11—C91 | 116.21 (17) | C12—N12—C92 | 116.27 (16) |
C61—N21—H21A | 112.8 (14) | C62—N22—H22A | 117.9 (12) |
C61—N21—H21B | 116.5 (13) | C62—N22—H22B | 117.7 (13) |
H21A—N21—H21B | 113.4 (18) | H22A—N22—H22B | 115.9 (17) |
N11—C11—C21 | 125.33 (17) | N12—C12—C22 | 125.15 (18) |
N11—C11—H11 | 117.3 | N12—C12—H12 | 117.4 |
C21—C11—H11 | 117.3 | C22—C12—H12 | 117.4 |
C11—C21—C31 | 121.54 (16) | C32—C22—C12 | 121.69 (16) |
C11—C21—C71 | 117.62 (15) | C32—C22—C72 | 120.70 (16) |
C31—C21—C71 | 120.84 (16) | C12—C22—C72 | 117.60 (16) |
C41—C31—C21 | 119.14 (17) | C42—C32—C22 | 119.07 (17) |
C41—C31—H31 | 120.4 | C42—C32—H32 | 120.5 |
C21—C31—H31 | 120.4 | C22—C32—H32 | 120.5 |
C31—C41—C51 | 120.61 (17) | C32—C42—C52 | 121.03 (17) |
C31—C41—H41 | 119.7 | C32—C42—H42 | 119.5 |
C51—C41—H41 | 119.7 | C52—C42—H42 | 119.5 |
C61—C51—C41 | 122.40 (17) | C62—C52—C42 | 122.09 (17) |
C61—C51—H51 | 118.8 | C62—C52—H52 | 119.0 |
C41—C51—H51 | 118.8 | C42—C52—H52 | 119.0 |
C51—C61—N21 | 121.04 (17) | N22—C62—C52 | 121.09 (17) |
C51—C61—C71 | 118.27 (16) | N22—C62—C72 | 120.84 (16) |
N21—C61—C71 | 120.47 (16) | C52—C62—C72 | 118.02 (16) |
C81—C71—C21 | 116.85 (15) | C82—C72—C22 | 116.72 (15) |
C81—C71—C61 | 124.42 (16) | C82—C72—C62 | 124.20 (16) |
C21—C71—C61 | 118.71 (16) | C22—C72—C62 | 119.08 (15) |
C91—C81—C71 | 119.98 (17) | C92—C82—C72 | 120.16 (17) |
C91—C81—H81 | 120.0 | C92—C82—H82 | 119.9 |
C71—C81—H81 | 120.0 | C72—C82—H82 | 119.9 |
C81—C91—N11 | 123.99 (18) | C82—C92—N12 | 124.09 (18) |
C81—C91—H91 | 118.0 | C82—C92—H92 | 118.0 |
N11—C91—H91 | 118.0 | N12—C92—H92 | 118.0 |
Cg1–Cg3 are the centroids of the N11/C11/C21/C71/C81/C91, C21/C31/C41/C51/C61/C71 and C22/C32/C42/C52/C62/C72 rings, respectively. |
D—H···A | D—H | H···A | D···A | D—H···A |
N21—H21A···N11i | 0.91 (2) | 2.19 (2) | 3.091 (2) | 179 (2) |
N22—H22A···N12i | 0.91 (2) | 2.18 (2) | 3.083 (3) | 173 (2) |
C91—H91···N22 | 0.95 | 2.55 | 3.419 (3) | 152 |
C92—H92···Cg1ii | 0.95 | 2.81 | 3.479 (2) | 128 |
C31—H31···Cg3iii | 0.95 | 2.63 | 3.423 (2) | 141 |
C32—H32···Cg2iv | 0.95 | 2.67 | 3.460 (2) | 142 |
Symmetry codes: (i) x+1/2, y−1/2, z; (ii) x+1/2, y+1/2, z; (iii) x−1/2, −y+3/2, z+1/2; (iv) x−1/2, −y+3/2, z−1/2. |
Experimental details
Crystal data | |
Chemical formula | C9H8N2 |
Mr | 144.17 |
Crystal system, space group | Monoclinic, Cc |
Temperature (K) | 150 |
a, b, c (Å) | 6.0731 (15), 14.921 (4), 16.285 (4) |
β (°) | 95.686 (4) |
V (Å3) | 1468.5 (7) |
Z | 8 |
Radiation type | Mo Kα |
µ (mm−1) | 0.08 |
Crystal size (mm) | 0.36 × 0.19 × 0.12 |
Data collection | |
Diffractometer | Bruker SMART CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS in SAINT-NT; Bruker, 2002) |
Tmin, Tmax | 0.98, 0.99 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 6002, 3082, 2701 |
Rint | 0.020 |
(sin θ/λ)max (Å−1) | 0.655 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.038, 0.090, 1.04 |
No. of reflections | 3082 |
No. of parameters | 215 |
No. of restraints | 9 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.15, −0.16 |
Computer programs: SMART (Bruker, 2001), SAINT (Bruker, 2002), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).
Cg1–Cg3 are the centroids of the N11/C11/C21/C71/C81/C91, C21/C31/C41/C51/C61/C71 and C22/C32/C42/C52/C62/C72 rings, respectively. |
D—H···A | D—H | H···A | D···A | D—H···A |
N21—H21A···N11i | 0.91 (2) | 2.19 (2) | 3.091 (2) | 179 (2) |
N22—H22A···N12i | 0.91 (2) | 2.18 (2) | 3.083 (3) | 173 (2) |
C91—H91···N22 | 0.95 | 2.55 | 3.419 (3) | 152 |
C92—H92···Cg1ii | 0.95 | 2.81 | 3.479 (2) | 128 |
C31—H31···Cg3iii | 0.95 | 2.63 | 3.423 (2) | 141 |
C32—H32···Cg2iv | 0.95 | 2.67 | 3.460 (2) | 142 |
Symmetry codes: (i) x+1/2, y−1/2, z; (ii) x+1/2, y+1/2, z; (iii) x−1/2, −y+3/2, z+1/2; (iv) x−1/2, −y+3/2, z−1/2. |
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We have previously reported the synthesis and structural analysis of compounds containing aromatic amines (Atria, Astete et al., 2011; Atria, Garland & Baggio, 2011, and references therein). In most of these structures, the amine groups are in complex with lanthanide or transition metal cations, and via their ability to promote nonbonding interactions of different types and strengths (hydrogen bonds, π–π interactions etc.) they ended up being the vectors for, usually, highly stable three-dimensional supramolecular structures.
On rare occasions, crystals of the free ligands were serendipitously obtained in addition to (or instead of) the expected complexes, and the analyses of their crystal structures were often worth discussing, not necessarily for the extractable molecular information (which was almost predictable beforehand) but rather for the extremely interesting three-dimensional networks they gave rise to. A representative case with diaminopurine can be found in Atria et al. (2010).
This report presents a further example of such an unexpected situation (see Experimental for details): the crystal structure of isoquinolin-5-amine, (I), a very simple molecule giving rise to an unusual supramolecular arrangement. It is worth mentioning that, in spite of its simplicity, this ligand is rare from a crystallographic point of view: only one entry in the Cambridge Structural Database (CSD, Version 5.33; Allen, 2002) could be found, with the ligand bonded to a ZnII nucleus [bis(isoquinolin-5-amine)diazido zinc(II), Zn(N3)2(C9H8N2)2, (II); Miao et al., 2007].
Compound (I) crystallizes in the monoclinic space group Cc with two independent molecules in the asymmetric unit (Fig. 1), which we will characterize hereinafter by the trailing digit in their labels (1 or 2). As stated above, the molecular details do not depart either from the usual values found in the CSD or between the two molecules. A few comparative details between the two independent units are: (i) least-squares molecular fitting, overall r.m.s. deviation = 0.018 Å and maximum deviation (for the N21···N22 pair) = 0.036 Å; (ii) bond distances, overall r.m.s. deviation = 0.004 Å and maximum deviation (for the N2x—C6x bonds) = 0.009 Å (2σ); (iii) bond angles, overall r.m.s. deviation = 0.222° and maximum deviation (for the C3x—C4x—C5x angles) = 0.44° (2σ).
Both isoquinoline nuclei (1 and 2) are planar [overall r.m.s. deviation = 0.0069 Å for both molecules; maximum deviations = 0.0140 (14) Å for C21 and 0.0118 (13) Å for C22], with the amino N atoms deviating significantly from the aromatic least-squares plane [0.161 (2) Å for N21 and 0.089 (2) Å for N22]. This deviation is accompanied by a substantial (though uneven) degree of pyramidality in the arrangement around them, evidencing an N-atom hybridization with a significant sp3 contribution for N21 and a more `flattened' arrangement around atom N22, suggesting a predominant sp2 character. If pyramidality is measured, as proposed by Allen et al. (1995), by χ(N), the angle between the C—N vector and its projection into the NH2 plane [ideal values: χ(N) = 0° for pure sp2; 54.7° for pure sp3], the corresponding values for both N atoms in the case of (I) are χ(N21) = 40.5° (mostly sp3) and χ(N22) = 28.6° (very nearly midway between sp3 and sp2). This is consistent with the C21—N21 bond [1.360 (2) Å] being slightly longer than the C22—N22 bond [1.350 (2) Å], suggesting a smaller delocalization in the former. This different degree of planarity of amino groups bound to aromatic nuclei is frequently found in the literature (e.g. Atria et al., 2010) and is usually ascribed to the variable ability of the delocalized π-system of the ring to accommodate charge from the amino group in the extended resonance structure, a fact probably conditioned by environmental factors such as coordination to a metal centre or hydrogen bonding.
As expected, the main interest of (I) resides in the way in which the supramolecular structure builds up. All the responsible noncovalent interactions are of the hydrogen-bonding type, with a diversity of donors (N—H and C—H) and acceptors (N and π), all of them shown in Table 1.
The two conventional N—H···N hydrogen bonds, appearing as the first two entries in Table 1, are by far the strongest and they define the two distinct motifs in the structure (Fig. 1), viz. two parallel chains, each one formed by a single type of molecule (either 1 or 2). These are in turn linked by a weak nonconventional C—H···N interaction (third entry in Table 1), which defines the hydrogen-bonded two-chain strips shown in Fig. 2 on a grey background and running along [110] (top to bottom in the figure). The H atoms involved in the main interactions (H21A and H22A) correspond to amino groups. Surprisingly, the remaining H atoms in each NH2 group are not involved in any type of hydrogen-bonding contact. This does not seem to be a particularly unusual effect: a search of the CSD showed that about 5% of the structures presenting aromatic amino units had their NH2 groups asymmetrically hydrogen-bonded, as found in (I).
The one-dimensional double-chain substructures are replicated by the c-glide plane into a second family of strips (Fig. 3), forming an angle of 44.32 (2)° with the former ones but now running along [110] and represented in Fig. 2 on a white background. These chains are seen exactly in projection in the figure (with the deceptive appearance of single molecules). One of these `vertical' [110] double-chain strips has been highlighted, for clarity.
Finally, these two families are connected via C—H···π intra- and inter-strip crosslinks (entries 4–6 in Table 1), which in Fig. 2 appear as `out-of-plane' bonds with the Cg acceptors (underlined labels in the figure), which are either above or below the plane.
As a final remark, we would like to introduce here a word of caution regarding the (frequently uncritical) geometric idealization of O—H and N—H atoms, a fact which can introduce gross interpretation errors in groups like NH2. An example can be found in the related Zn complex, (II), where this simplistic assumption was made in the published results, thus making impracticable any possible comparison with our own results. Taking advantage of the fact that the data set of (II) looked fair {Rint = 0.036 and R[F2 > 2σ(F2)] = 0.029} and that the structure factors were available in the literature, we performed a new refinement of the structure of (II) with the amino H atoms subject to the same restraints as we applied for (I). To our surprise, an even more enhanced pyramidalization trend was observed around the amino N atoms in the two independent isoquinolin-5-amine units, with two strongly dissimilar degrees of sp2–sp3 hybridization and a similar tendency as in (I) in the corresponding C—N bond distances [χ: 15.9 and 40.7°; C—N: 1.358 (4) and 1.385 (3) Å]. The convenience of confirming the H-atom structure through a careful analysis of the difference maps thus becomes apparent.